High-frequency mechanical spectroscopy with an atomic force microscope

In this article we further develop local mechanical spectroscopy and extend the frequency range over which it can be used. Using a heterodyne method to measure the deflection of the cantilever enables one to measure the probe vibration at any frequency. Since the detection sensitivity of force gradients follows a f2 dependence, extending the frequency range from 1 to more than 5 MHz increases the sensitivity by over an order of magnitude. This setup is combined with a realistic model of the cantilever taking into account the geometry of the cantilever. The model is presented and discussed, and compared with experimental behavior measured on WC–Co and NiTi–epoxy samples. Experimental moduli of 730±50 and 260±40 GPa are obtained for WC and Co, respectively.